I pulled a ripped bellows off of a Duet a couple of weeks ago. Homeowner was standing there. When I flipped it over and showed her solid black with stinking mold, she almost had a corony. Asked me what she could do, and I told her to change the boot every couple of years. She said she wanted me to change it in two years if I could schedule it. Done. I hope to get a few more like this.